| Message ID | 20160809190229.27871-1-bobby.prani@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 09/08/2016 21:02, Pranith Kumar wrote: > From: Paolo Bonzini <pbonzini@redhat.com> > > With the latest clang, we have the following warning: > > /home/pranith/devops/code/qemu/include/qemu/seqlock.h:62:21: warning: passing 'typeof (*&sl->sequence) *' (aka 'const unsigned int *') to parameter of type 'unsigned int *' discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers] > return unlikely(atomic_read(&sl->sequence) != start); > ^~~~~~~~~~~~~~~~~~~~~~~~~~ > /home/pranith/devops/code/qemu/include/qemu/atomic.h:58:25: note: expanded from macro 'atomic_read' > __atomic_load(ptr, &_val, __ATOMIC_RELAXED); \ > ^~~~~ > > Stripping const is a bit tricky due to promotions, but it is doable > with either C11 _Generic or GCC extensions. Use the latter. > > Reported-by: Pranith Kumar <bobby.prani@gmail.com> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > [pranith: Add conversion for bool type] > Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> > --- > include/qemu/atomic.h | 54 +++++++++++++++++++++++++++++++++++++++++++++------ > 1 file changed, 48 insertions(+), 6 deletions(-) > > diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h > index 7e13fca..43b0645 100644 > --- a/include/qemu/atomic.h > +++ b/include/qemu/atomic.h > @@ -18,6 +18,48 @@ > /* Compiler barrier */ > #define barrier() ({ asm volatile("" ::: "memory"); (void)0; }) > > +/* The variable that receives the old value of an atomically-accessed > + * variable must be non-qualified, because atomic builtins return values > + * through a pointer-type argument as in __atomic_load(&var, &old, MODEL). > + * > + * This macro has to handle types smaller than int manually, because of > + * implicit promotion. int and larger types, as well as pointers, can be > + * converted to a non-qualified type just by applying a binary operator. > + */ > +#define typeof_strip_qual(expr) \ > + typeof( \ > + __builtin_choose_expr( \ > + __builtin_types_compatible_p(typeof(expr), bool) || \ > + __builtin_types_compatible_p(typeof(expr), const bool) || \ > + __builtin_types_compatible_p(typeof(expr), volatile bool) || \ > + __builtin_types_compatible_p(typeof(expr), const volatile bool), \ > + (bool)1, \ > + __builtin_choose_expr( \ > + __builtin_types_compatible_p(typeof(expr), signed char) || \ > + __builtin_types_compatible_p(typeof(expr), const signed char) || \ > + __builtin_types_compatible_p(typeof(expr), volatile signed char) || \ > + __builtin_types_compatible_p(typeof(expr), const volatile signed char), \ > + (signed char)1, \ > + __builtin_choose_expr( \ > + __builtin_types_compatible_p(typeof(expr), unsigned char) || \ > + __builtin_types_compatible_p(typeof(expr), const unsigned char) || \ > + __builtin_types_compatible_p(typeof(expr), volatile unsigned char) || \ > + __builtin_types_compatible_p(typeof(expr), const volatile unsigned char), \ > + (unsigned char)1, \ > + __builtin_choose_expr( \ > + __builtin_types_compatible_p(typeof(expr), signed short) || \ > + __builtin_types_compatible_p(typeof(expr), const signed short) || \ > + __builtin_types_compatible_p(typeof(expr), volatile signed short) || \ > + __builtin_types_compatible_p(typeof(expr), const volatile signed short), \ > + (signed short)1, \ > + __builtin_choose_expr( \ > + __builtin_types_compatible_p(typeof(expr), unsigned short) || \ > + __builtin_types_compatible_p(typeof(expr), const unsigned short) || \ > + __builtin_types_compatible_p(typeof(expr), volatile unsigned short) || \ > + __builtin_types_compatible_p(typeof(expr), const volatile unsigned short), \ > + (unsigned short)1, \ > + (expr)+0)))))) > + > #ifdef __ATOMIC_RELAXED > /* For C11 atomic ops */ > > @@ -54,7 +96,7 @@ > #define atomic_read(ptr) \ > ({ \ > QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ > - typeof(*ptr) _val; \ > + typeof_strip_qual(*ptr) _val; \ > __atomic_load(ptr, &_val, __ATOMIC_RELAXED); \ > _val; \ > }) > @@ -80,7 +122,7 @@ > #define atomic_rcu_read(ptr) \ > ({ \ > QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ > - typeof(*ptr) _val; \ > + typeof_strip_qual(*ptr) _val; \ > atomic_rcu_read__nocheck(ptr, &_val); \ > _val; \ > }) > @@ -103,7 +145,7 @@ > #define atomic_mb_read(ptr) \ > ({ \ > QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ > - typeof(*ptr) _val; \ > + typeof_strip_qual(*ptr) _val; \ > __atomic_load(ptr, &_val, __ATOMIC_RELAXED); \ > smp_rmb(); \ > _val; \ > @@ -120,7 +162,7 @@ > #define atomic_mb_read(ptr) \ > ({ \ > QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ > - typeof(*ptr) _val; \ > + typeof_strip_qual(*ptr) _val; \ > __atomic_load(ptr, &_val, __ATOMIC_SEQ_CST); \ > _val; \ > }) > @@ -137,7 +179,7 @@ > > #define atomic_xchg(ptr, i) ({ \ > QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ > - typeof(*ptr) _new = (i), _old; \ > + typeof_strip_qual(*ptr) _new = (i), _old; \ > __atomic_exchange(ptr, &_new, &_old, __ATOMIC_SEQ_CST); \ > _old; \ > }) > @@ -146,7 +188,7 @@ > #define atomic_cmpxchg(ptr, old, new) \ > ({ \ > QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ > - typeof(*ptr) _old = (old), _new = (new); \ > + typeof_strip_qual(*ptr) _old = (old), _new = (new); \ > __atomic_compare_exchange(ptr, &_old, &_new, false, \ > __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); \ > _old; \ > Queued patches 1, 3, 4. Paolo
diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h index 7e13fca..43b0645 100644 --- a/include/qemu/atomic.h +++ b/include/qemu/atomic.h @@ -18,6 +18,48 @@ /* Compiler barrier */ #define barrier() ({ asm volatile("" ::: "memory"); (void)0; }) +/* The variable that receives the old value of an atomically-accessed + * variable must be non-qualified, because atomic builtins return values + * through a pointer-type argument as in __atomic_load(&var, &old, MODEL). + * + * This macro has to handle types smaller than int manually, because of + * implicit promotion. int and larger types, as well as pointers, can be + * converted to a non-qualified type just by applying a binary operator. + */ +#define typeof_strip_qual(expr) \ + typeof( \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(typeof(expr), bool) || \ + __builtin_types_compatible_p(typeof(expr), const bool) || \ + __builtin_types_compatible_p(typeof(expr), volatile bool) || \ + __builtin_types_compatible_p(typeof(expr), const volatile bool), \ + (bool)1, \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(typeof(expr), signed char) || \ + __builtin_types_compatible_p(typeof(expr), const signed char) || \ + __builtin_types_compatible_p(typeof(expr), volatile signed char) || \ + __builtin_types_compatible_p(typeof(expr), const volatile signed char), \ + (signed char)1, \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(typeof(expr), unsigned char) || \ + __builtin_types_compatible_p(typeof(expr), const unsigned char) || \ + __builtin_types_compatible_p(typeof(expr), volatile unsigned char) || \ + __builtin_types_compatible_p(typeof(expr), const volatile unsigned char), \ + (unsigned char)1, \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(typeof(expr), signed short) || \ + __builtin_types_compatible_p(typeof(expr), const signed short) || \ + __builtin_types_compatible_p(typeof(expr), volatile signed short) || \ + __builtin_types_compatible_p(typeof(expr), const volatile signed short), \ + (signed short)1, \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(typeof(expr), unsigned short) || \ + __builtin_types_compatible_p(typeof(expr), const unsigned short) || \ + __builtin_types_compatible_p(typeof(expr), volatile unsigned short) || \ + __builtin_types_compatible_p(typeof(expr), const volatile unsigned short), \ + (unsigned short)1, \ + (expr)+0)))))) + #ifdef __ATOMIC_RELAXED /* For C11 atomic ops */ @@ -54,7 +96,7 @@ #define atomic_read(ptr) \ ({ \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ - typeof(*ptr) _val; \ + typeof_strip_qual(*ptr) _val; \ __atomic_load(ptr, &_val, __ATOMIC_RELAXED); \ _val; \ }) @@ -80,7 +122,7 @@ #define atomic_rcu_read(ptr) \ ({ \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ - typeof(*ptr) _val; \ + typeof_strip_qual(*ptr) _val; \ atomic_rcu_read__nocheck(ptr, &_val); \ _val; \ }) @@ -103,7 +145,7 @@ #define atomic_mb_read(ptr) \ ({ \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ - typeof(*ptr) _val; \ + typeof_strip_qual(*ptr) _val; \ __atomic_load(ptr, &_val, __ATOMIC_RELAXED); \ smp_rmb(); \ _val; \ @@ -120,7 +162,7 @@ #define atomic_mb_read(ptr) \ ({ \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ - typeof(*ptr) _val; \ + typeof_strip_qual(*ptr) _val; \ __atomic_load(ptr, &_val, __ATOMIC_SEQ_CST); \ _val; \ }) @@ -137,7 +179,7 @@ #define atomic_xchg(ptr, i) ({ \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ - typeof(*ptr) _new = (i), _old; \ + typeof_strip_qual(*ptr) _new = (i), _old; \ __atomic_exchange(ptr, &_new, &_old, __ATOMIC_SEQ_CST); \ _old; \ }) @@ -146,7 +188,7 @@ #define atomic_cmpxchg(ptr, old, new) \ ({ \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \ - typeof(*ptr) _old = (old), _new = (new); \ + typeof_strip_qual(*ptr) _old = (old), _new = (new); \ __atomic_compare_exchange(ptr, &_old, &_new, false, \ __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); \ _old; \